Sterilization is the act of killing bacteria and other microorganisms on surgical instruments, devices and implants. Sterilizers are designed to kill all viable living organisms within a sterilization chamber. This is challenging, as objects can be contaminated with any of a number of different types of bacteria, some more dangerous and tougher to kill than others.
Sterilization indicators show whether a sterilizer achieved adequate (e.g. lethal) conditions. One kind of sterilization indicator is known as a chemical indicator. Chemical indicators respond to one or more of the critical parameters of a sterilization process. Typically, chemical indicators either change color or have a moving front with an endpoint to provide information concerning the sterilization process.
The Association for the Advancement of Medical Instrumentation {AAMI} has recommended practices and standards that cover sterilization testing, including the use of chemical indicators. Hospitals frequently look to AAMI to establish sterilization assurance procedures. See e.g. Good Hospital Practice: Steam Sterilization and Sterility Assurance, AAMI Recommended Practice, Section 6.4 (1988). Hospitals also look to other standards and regulatory agencies for validation, routine control and other procedures for obtaining, recording, and interpreting data to show that a sterilization process complies with a predetermined sterility assurance level. Other recommendations and guidelines are provided by the Joint Commission on Accreditation of Hospitals (JCAH), the Center for Disease Control, Association of Operating Room Nurses (AORN), American Society for Healthcare Central Services Personnel (ASHCSP), and the various state laws.
AAMI categorizes chemical indicators in five classes. See Sterilization of health Care Products—Chemical Indicators—Part 1: General Requirements, American National Standards Institute (ANSI)/AAMI ST 60-(1996). Class 1 relates to process indicators. Process indicators are intended for use with individual packs to demonstrate that the pack has been exposed to the sterilization process and to distinguish between processed and unprocessed packs. Class 2 describes indicators for use in a specific test procedure such as a Bowie-Dick test. Class 3 relates to single parameter indicators, and class 4 to multi-parameter indicators. Multi-parameter indicators are designed to respond to two or more critical parameters of sterilization and indicate exposure to a sterilization cycle at stated values of the chosen parameters. For example, time, temperature and saturated steam are critical conditions for a steam cycle. Class 5 chemical indicators are known as integrating indicators. These are indicators designed to react to all critical parameters over a specific range of sterilization cycles.
Integrating chemical indicators are described in U.S. Patent Reexamination Certificate No. B1-3,981,683, (Larsson et al.) and U.S. Patent Reissue No. 34,515 to Foley. Other chemical indicators are described in U.S. Pat. Nos. 3,114,349; 3,313,266; 3,341,238; 3,652,249; 4,138,216; 4,382,063; 4,576,795; 4,692,307; 4,579,715; and 5,451,372 (the entire contents of each of which are herein incorporated by reference).
Another kind of sterilization indicator is known as a biological indicator. Biological indicators use a large number (usually a million or more) of microorganisms that are highly resistant to the sterilizing agent of the sterilization cycle being monitored. See Sterilization of Health Care Products—Biological Indicators—Part 1: General Requirements, ANSI/AAMI ST 59 (incorporated herein by reference). Biological indicator technology is also disclosed in U.S. Pat. Nos. 3,661,717 and 5,073,088 (the entire contents of which are herein incorporated by reference).
Minnesota Mining and Manufacturing Company (3M) sells Attest™ Rapid Readout Biological Monitoring Systems. These systems include a biological indicator that is capable of exhibiting fluorescence after a failed (non-lethal) sterilization cycle, and an auto reader. To test a steam sterilizer with an Attest system, the user places the biological sterilization indicator into the steam sterilizer along with the items to be sterilized. After the sterilization cycle, the indicator is placed in an Attest auto reader (e.g. model 190). The auto reader has an incubator and a means for reading the biological indicator to determine whether the sterilization indicator exhibits fluorescence. If the steam sterilization cycle was lethal, the auto reader will not detect fluorescence within a predetermined time. If the cycle was non-lethal, the auto reader will detect fluorescence associated with the biological sterilization indicator in the predetermined time. Even with this instrumentation, a user is required to manually record the results provided by the auto reader.
Other international standards organizations and regulatory agencies describe sterilization indicators for monitoring sterilization processes in the health care context. The International Organization for Standardization (ISO) includes many standards similar to those described above. See ISO 11140-1:1995 for chemical indicators. European Standard Nos. EN 867-1 and 866-1 also include many standards similar, but not identical to those of AAMI and ISO (see e.g. The European Committee for Standardization's European Standard No. EN 867-1, Non-biological systems for use in sterilizers—Part 1: General requirements).
When a U.S. hospital designs its sterilization assurance practices, it often evaluates equipment control, exposure control, pack control and load control. Equipment control evaluates sterilizer performance. For example, a Bowie-Dick pack can indicate the failure of the vacuum portion of a steam sterilization cycle. Load control is often a biological indicator placed in the sterilization chamber.
Items to be sterilized are often wrapped in sterilization wrap. The wrap is typically secured with an exposure control indicator (e.g. indicator tape). The resultant assembly is referred to as a pack. Exposure control is typically a chemical indicator placed within the sterilization chamber but outside the pack that is being sterilized. Exposure control identifies processed from unprocessed packs. Pack control is usually a sterilization indicator placed within a pack that evaluates conditions inside an individual pack. After a successful sterilization cycle, the articles within the sterilization packs remain sterile until the pack is opened. As a result, packs are usually opened in a specially prepared and maintained sterile field in the operating room just prior to their use. However, commercially available sterilization indicators found within packs cannot be read prior to opening the pack because sterilization wrap is typically opaque. If the sterilization indicator inside a pack indicates a failed sterilization cycle, there are many problems in finding out about it just prior to use of the items within the pack. The problems are multiplied when the sterilization indicator identifying a failure is found within the specially prepared and maintained sterile field.
The importance of sterilization assurance in hospitals requires constant attempts to better utilize sterilization indicators. A user typically visually inspects chemical indicators to obtain information from the indicator. Some users find it difficult to subjectively determine whether a chemical indicator has changed color. This is particularly a problem for a user who suffers from color blindness. For example, some persons who suffer from color blindness have difficulty distinguishing red colors from green colors. The Propper Gas-Chex® Steri-Dot Indicators (Model No. 361001) change from a red color to green upon exposure to ethylene oxide gas. This color change may be difficult for some users to distinguish with the attendant risk of inaccurate recordation of sterilization information. Another indicator with a color change that is difficult to perceive is the Surgicot® Version 3.0 Universal Integrator. This integrator includes a steam color change bar from yellow to brown. The contrast between these particular colors is difficult for some users to perceive.
Biological indicators suffer from some of the same problems as chemical indicators. U.S. Pat. Nos. 5,030,832; 5,063,297; 5,334,841 and 5,863,790 (the entire contents of each of which are herein incorporated by reference) describe electronic reading apparatus for objectively reading fluorescence of biological indicators.
Accuracy of information relating to the state of objects in the sterilization process at a healthcare facility (e.g. a hospital) is very important. Access to this information is also important. There are many ways that human error can adversely affect a hospital's sterilization assurance procedures. Operators can err in capturing data (e.g. transpose numbers, improperly key-in information to a computer), perceiving information (e.g. the color blindness issue discussed above) and recording data, to name just a few. Because sterilization indicators are small, they can simply become lost, especially if their use entails transportation between different hospital functions, locations or departments.
Despite the importance of this information and the problems noted above, the recordation or management of information relating to sterilization in U.S. hospitals today usually includes several subjective, manual steps. For example, forms are manually filled out with a pen or pencil, or a sterilization indicator is subjectively inspected for color change, or the information is manually typed into a database. When a hospital utilizes several different types of sterilizers (e.g. steam sterilizers, flash steam sterilizers, ethylene oxide sterilizers or vapor phase hydrogen peroxide sterilizers), it makes the recording problem even more complex. To address the problems mentioned above, hospitals invest in significant and costly training of personnel responsible for sterilization monitoring.
There are many sterilization article tracking systems reported in the literature. U.S. Pat. No. 3,568,627 discloses a combined record card and sterilization indicator. German Utility Model (Gebrauchsmuster) No. G 90 04 818.0 (assigned to Vereinigte Papierwarenfabriken GmbH) discloses a label for sterile packaging. However, these require manual steps associated with the sterilization information tracking.
Bar codes are used extensively in the health care industry. See Adams et al., Bar Coding: An Effective Productivity Concept, JONA, Vol. 21, No. 10 (October 1991); and Weilert et al., Putting Bar Codes to Work for Improved Patient Care, Clinics in Laboratory Medicine, Vol. 11, No. 1 (March 1991). German Patent Application No. DE 3917876 discloses a bar code on a surgical instrument. U.S. Pat. No. 5,635,403 describes a tracking and identification card for an air filter specimen that includes a bar code. U.S. Pat. No. 5,653,938 discloses bar codes used in a method for ensuring sterility of surgical drapes. Such bar codes comprise a permanent, colorfast black ink, as opposed to a sterilizing agent sensitive ink (e.g. one that changes colors during a sterilization cycle).
European Patent Application No. 630 820 discloses a process and system for monitoring material flow during the preparation of sterile goods. This inventory system utilizes bar codes to help track objects to be sterilized. U.S. Pat. Nos. 5,374,813 and 5,610,811 describe surgical instrument tracking systems that make use of bar codes. None of these bar codes include a sterilizing agent sensitive ink.
Some hospitals utilize computerized inventory management systems that require a user to manually key in data relating to the status of a sterilization indicator. For example, in the same sterilization load, a biological indicator, chemical indicators and a test pack may be used. The prior art inventory management systems require the user to manually input a great deal of data relating to these different types of sterilization indicators with the attendant risk that the user will improperly record the information or fail to record it at all. For example, a user may manually type in information relating to whether the indicator shows “pass” or “fail” of the sterilization cycle. The difficulty associated with accurately recording sterilization information is exacerbated by the fact that chemical indicator information is typically recorded just after a sterilization cycle while biological indicator information is recorded many hours or days after the sterilization cycle.
The art is also replete with electro-optical devices for reading items. Examples of such devices are described in U.S. Pat. Nos. 5,351,078; 5,576,528 and 5,619,029. Canadian patent No. 1,204,300 (Prusik et al.) describes an electro-optical device for reading a bar code. The bar code is said to be useful for, inter alia, assessing time-temperature exposures of environmental indicating devices that are attached to products which experience progressive quality changes as they are subjected to certain temperatures over certain periods of time. Prusik et al. does not disclose a chemical indicator for use in monitoring a sterilization procedure at a health care facility.
Sterilization indicators and labels for articles to be sterilized are typically manufactured at a location remote from their actual use. Thus, the type and design of sterilization indicators are dictated by the manufacturer, not by users. Moreover, users do not have the ability to generate their own indicators. As a result, hospitals today are required to order and ship very specific types of indicators that are not hospital/site specific. There is little chance for customization of the indicator at the hospital. As a result, some hospitals even customize information on existing labels with manual printable pens to capture information such as pack content, intended location and targeted use.